Telephone system



Dec- 23, 1941- H. E. voN KNIG 2,267,178

' TELEPHONE SYSTEM l File'd Aug. 25, 1939 5 Sheets-Sheet l Beg-23, 1941 v H.. E. VN KNlG 2,267,178

TELEPHONE l SYSTEM x Filed Aug. 25, V1939 5 sheets-sheet 2 524121 V/ 7 I /RL l l2131111, ,2mn 16151 jg ,1gb/1 A fr0/MEV Dec. 23, 1941.

H. E. voN KNIG 2,267,178

TELEPHONE SYSTEM Filed Aug. 25, 1959 5 sheets-sheet 4 F- IE 4 awa /vasb wa' Dec.z3, 1941. H. E. vVONKCSNIG Q 2,267,178

TELEPHONE SYSTEM Filed Aug.' 25, 1939 5 sheets-sheet 5 FIL-:1 5,;

'l 941,1 /96114 AW Dr5 Il Patented Dec. 23, 1941 TELEPHONE SYSTEM Hermann Ernst von Knig, Berlin-Johannisthal, Germany, assignor to Fides Gesellschaft fr die Verwaltung und Verwertung von gewerblichen Schutzrechten mit beschrnkter Haftung, Berlin, Germany, a corporation of Germany Application August 25, 1939, Serial No. 291,798

In Germany August 29, 1938 v 7 Claims.

In automatic telephone installations with a number of exchanges and in particular in private exchanges, it is often required to extend all highvalued connections with other telephone systems, i. e. exchange connections, over a particular exchange which is the main exchange. High-valued connections to and from subscribers of the other exchanges (sub-exchanges) musi-l therefore be set up over connecting arrangements of at least two exchanges.

If subscribers with diierent traine facilities are connected to these installations, e. g. private exchange stations and house telephone stations, and if moreover it is to be possible to sei' up revertive connections, then in setting up highvalued connections to and from subscribers of the sub-exchange considerable diiiiculties are experienced in testing the trac facilities of the subscriber for the outgoing and incoming connections. revertive switching is carried out in the calling subscribers exchange, or in another exchange over which the high valued-connections extend, according to the traic direction.

It has already been proposed in such telephone systems to determine the trame facilities of the subscriber of a sub-exchange according to the traino direction of the existing high-valued connection either in the sub-exchange or in th'e main exchange. The determination of the tralTic facilities is performed for out-going connections by means of the discriminator in the sub-exchange and for incoming connections by means of a special selector connected in the main exchange in the talking connection and provided specially During the setting up of a connection for this purpose. When a subscriber of the subexchange initiates a revertive connection and if the required subscriber is connected to the` main exchange, then the impulse for carrying out the revertive connection in the main exchange is given by means of a numerical impulse receiver situated in the sub-exchange in the revertive path. Economically, this is only possible when between the main and sub-exchanges only one cross connecting line is present since, when there y which high-valued connections are always extended over a main exchange, so that for testing the traflic facilities of the subscriber in the subexchange and for carrying out a revertive connection in the main exchange under the control of a subscriber of the sub-exchange the considerable complication due to different connecting apparatus, in particular, the provision of special wipers, is avoided. To obtain this result, discriminators are provided in an exchange at which, for high-Valued connections junction lines to other systems, e. g. to a public exchange, are not completed for use, which discriminators control switch means, when a high-valued connection is set up, for determining the traffic facilities of a subscriber of the exchange and, when revertive connections are set up', control switch means in another exchange under the control of the marking operation by means'of the revertively calling subscriber which Vbring. about a revertive connection at the other exchange.

Since a single discriminator may control the testing of the traine facilities and the control of the revertive connected station it is not necessary to provide the connecting apparatus of the exchange with extra wipers over'and above those which are necessary for setting up and maintaining th'e connection. Testing operations and removal of disturbances can be rapidly performed since the switching operations in question are always controlled from one station by the discriminator.

The drawings show .those connecting and control arrangements of a private telephone system, consisting ofl a main exchange HZ and an unsupervised sub-exchange UZ, which are necessary for the understanding of the invention.

By revertive enquiry connection is meant a connection set up by a subscriber who is already in an established connection and desires to hold the established connection and revert the call to another subscriber for the purpose of making an equiry, after which the enquiry connection is released and the original connection reestablished to report the result of the enquiry.

f In Figures 1, 2 and 3 arrangements for the sub-exchange UZ are shown and in Figures 4 and 5 arrangements for the main exchange HZ.

Before the individual connections are explained the general features of th'e installations will be indicated.

In the main exchange HZ the two-Way exchange lines AL are terminated. 'I'he main and sub-exchanges are connected by a number of junctions (VL) over which the exchange traffic permissible, and determines the revertive switchj ing station to which the required subscriber is connected when setting up a revertive connection under the control of the exchange over which the enquiry connection must extend. If a subscriber of the sub-exchange sets up a local connection to the subscriber of the main exchange, the discriminator is positioned by means of numerical impulses but performs no switching operations. In local connections/from the main to sub-exchanges the discriminator is not positioned by means of the numerical impulses.

In the embodiment shown in each of the two exchanges HZ and MZ pre-selectors and final selectors are used. In one exchange and also in both exchanges, one or more group selectors or finder switches can be used in place of preselectors and also primary and secondary line finders instead of simple pre-selectors. The selector equipment of the exchanges is not related to the subject of the invention.

I. Setting up of an archange connection by the subscriber TnNl of the sub-exchange The calling subscriber TnNI is connected by means of the selector NVWI associated with his line and a further selector NLWI with a free junction to the main exchange HZ. In the seizing circuit: test relay, not shown, in the rst selector NLWI, Wiper contact 2, conductor 3, relay CI, contacts 4k, Sph, 6i, resistance relay CI operates with a delay in view of the short circuit by contact 8cl and resistance 9 so that before the operation of its contact the talking conductors are switched through in the final selector NLWI and the feeding bridge relay A2 of the seized access means to the junction line operated in the microphone feeding circuit. At contact Illa-2 relay I2 is connected. Contact Ila2 in the access means to the conductor Ib to the junction VL is closed so that after the operation of relay CI and opening of contacts |2cl, |3c| as well as the closing of contacts |4c|, I5c| minus is connected to both conductors la and Ib of the junction VL. At contact 580| the circuit for the rotary magnet DML of the junction VL is prepared in the discriminator associated with the sub` exchange UZ.

Over the conductor lb the seizing impulse is transmitted to the main exchange: relay Dr?, contacts IIaZ, |5cl, conductor lb, contacts |Bw3. |103, relay I3, The relay I3 by opening Contact |4113 guards the junction VL against seizing over the selector of the main exchange. It connects the relay V4; contacts |8'i3, |9n, 2fla3, relay V4, resistance 2|, At contact 22114 relay B (winding I) is connected. At contact 2lb the circuit extending over contact 28u73 for the relay KI is closed. The contact |4817 in series with the contact |41i3 is opened in the seizing circuit. Simultaneously relay P3 is also operated: in the final selector LW2 associated with the junction, contacts not shown in this selector, contacts 23174, 2533, relay P3, contact 2603, At Contact 29p3, the relay P3 locks up independently of contact 23114 and 25s3 in a circuit which is dependent on the contacts in the iinal selector LW2 not shown. At contact 30113 and 3|p3 the talking conductors to the iinal selector LW2 over which the numerical impulses are also transmitted are switched through.

The impulse receiver of the nal selector LW2 not shown which bridged the talking conductors operates in the circuit over contacts 30213, 94ul, choke Dr5, contacts 4613, M, 3|p3 and carries out the known switching operations which make possible the setting of the iinal selector by means of numerical impulses. The relay Phl is connected: -1, contacts 32113, 33c4, 34114, relay PHI, At Contact 351ml one conductor of the access means to a junction line VL from the nal selector of the main exchange HZ is opened and at contact 36ph| a circuit is closed over the conductor la over the junction VL: contact 36pm, relay M3, Contact 31H or 270124, conductor la, contacts 38w2, 39wl, I4cl, relay M2, Both relays M3 in the main exchange and M2 in the sub-exchange operate.

In the main exchange relay S3 is connected: contacts 401ml, 4|m3, relay S3, At contact 4283 it locks up dependent on Contact 43h. The closing of contact 44s3 in series with the choke D15 is without significance since contact 45n is opened.

In the sub-exchange UZ relay M2 has completed at contact 4'lm2 the energising circuit for relay K prepared at contact 480| and extending over relay CI and the test relay of the final selector NLWI. Relay K locks up at contact 49k, opens the original energising circuit for relay CI at contact 4k and by closing contact 50k prepares the short circuit of the relay CI which comes into erlect on the release of the connection when contacts 5|a2 and 52m2 are closed continuously. For the time being contacts 5|a2 and 52m2 are opened.

Relay M2 also connects relay E: rotary magnet DML, control relay V, principal contact of the discriminator 53lcml, winding I of relay E, contact 21h), 5582, 561112, Only relay E operates. It closes contact 51e in the energising circuit or rotary magnet DML still open at contact 6Ii2.

The calling subscriber TnNI transmits the marking digit, for example 0, for impulse trains corresponding to the exchange connection (l0 impulses). 'I'hese impulses are eiective on the relay A2 which by means of contact |0a2 controls the impulse repeating relay I2 and by means of the contact I Ia2 transmits the impulses to the impulsing relay I3 in the main exchange HZ. The relay I3 by means of its contact 46i3 transmits the impulses to the impulsing relay, not shown, in the nal selector LW2 which is thus stepped up to the fourth bank. The further switching operations in the main exchange are explained later.

In the sub-exchange relay I2 on each release closes the circuit for rotary magnet DML: contacts 58cl, 51e, 590|, 60a, 6|z2, control relay V, rotary magnet DML, The control relay V is energised and maintains its armatures operated during the impulse train. At contact 2'||v it opens the energising circuit over the winding I of relay E and at contact 62o closes a holding circuit over winding II of this relay. On the first rotary step of the discriminator the offnormal contact 537mm is opened and the oinorrnal contact 547cm| closed. The relay E has opened contacts 63e, 64e, 65e and therefore during the positioning of the'selector over the wipers ML/H, ML/V and ML/A switching operations cannot be performed. On the rst release of relay A2 relay V2 is connected: contacts 66c|, 61112, relay V2, The contacts 68122, 6902 are opened and contacts 10112, 1h22 closed.

At the end of the impulse transmission and when contacts 6li2 and 61a2 are maintained open relays V, V2 and E restore. Over the discriminators set corresponding to the marking digit for exchange connections, the traffic facilities of the calling subscriber are now det-ermined. For this purpose over the wiper ML/A relay S2 is connected: contacts 12cl, 65e, wiper NIL/A, contact 13, relay S2, Relay S2 locks up at contact 1452 independently of contact 65e, wiper ML/A and contact 13, until the release of the connection, and at contacts 1582 and 1682 it opens the short circuit for windings I and II of the dilerence relay X2 in series with relay A2 and further opens the contact 1152 in the seizing conductor 98 which can only be reached over the final selector HLWI, with which only the group of subscribers (local stations) which are not authorized for exchange connections are associated- The effect of contact 1182 is explained later.

The energising of relay S2 results in the immediate setting of the discriminator to its normal position. The circuit for the magnet DML and the control relay V is completed: magnet DML, relay V, oi-normal contact 34kml, contacts 18e, 19e, 80h, 8152, The discriminator steps on by one step. Over the contact 82dml relay E (winding II) is energised and at contact 18e opens the circuit for the driving magnet DML and the control relay V. The rotary magnet restores more quickly than the control relay and disconnects the winding II of relay E. This interaction between the magnet DML and the relay E continues until the discriminator has reached the normal position In this position the oiT-normal contact 547cm| is opened and the energising circuits for DML and V can no longer be closed. Also on the release of relay V further closing of the circuit for magnet DML is not possible over the olf-normal contact 53kml since the contacts 83e, 5532 and I53h in series with contact 21h; are opened.

In the main exchange' after the setting of the final selector by means of the impulse train corresponding to the marking digit for exchange connection over a contact of the final selector, e. g. over bank-contact or as shown over a bank contact of the selecting group on to which the nal selector automatically rotates, the relay Ul is energised: test relay P4, wiper 84 and' contact 85 of the nal selector LW2, contact Stel, winding I of relay UI, Parallel to winding I the resistance 88 is connected over the contact 81ul. The relay Ul operates and is slow-to-energise. It closes a circuit over winding I of relay EI: contacts 89u13, Sul, relay El, winding I, At contact 9Ie| a holding circuit is set up over winding II of relays El and UI: contacts 92M, 9lel, winding II of relay El, and contact 931/3, winding II of relay Ui At contacts Sflul and Sul the conductors extending to the final selector LW2 are disconnected from the junction VL. The latter is connected over contacts Blul and 91u] with the conductors which extend to the exchange selector AW. As the exchange selector instead of distributors nder switches can also be used.

On the opening of contacts Mul, 95u! the re- 3 lays in the nal selector LW2 bridging the talking conductors restore and bring about the re-v lease of the nal selector By means of the control arrangements -4- is thus disconnected from the holding relay.P3 so that the contacts 30113 and 3I'p3 are opened y In bridge between the conductors extending to the exchange selector AW the choke Dr' is now connected over contact 46i3. The exchange selector AW selects a free outgoing exchange line AL, The bridge relay S4 is energised in the circuit extending oVer the choke Dr5 and brings about the known switching operations necessary for the further setting up of the exchange connection. The diierence relay X4 is not energised.

By means of the contact 432'3 the impulses transmitted for the calling subscriber and serving to set the selector in the public exchange are repeated to the impulse repeating relay Sd which transmits these impulses to the impulse receiving apparatus in the selectors of the public exchange. f

At the end of the connection the release of the connecting arrangements in the private exchange system (HZ, UZ) is performed in the usual manner when the subscriber TnNl hangs up his receiver and causes the feeding bridge to restore.

II. The subscriber TnHI initiates an exchange connection In addition to the subscribers (suoli as TnNi) Aauthorized for exchange connections subscribers are included in the sub-exchange UZ who f may only set up connections with subscribers of the private system. The subscriber TnI-II repre-` sents such a local station.

It is assumed that the private stations and the local stations do not use the same numerical impulse receiver but that for each subscriber group a selector group (NLW for` private stations, HLW for local stations) is provided. `It is understood that both groups of subscribers haveaccess to the same numerical impulse receivers and dependent on the equipment of the subscribers circuit in the exchange the traffic facilitiesof the calling subscriber to the laccess means of the junction are marked.

When the subscriber TnHl vmakes a call the preselector HVWl seizes a free final selector HLWI which is positioned by means of numerical impulse trains corresponding to the marking digits for connections over main exchange HZ andv thereupon seizes a free junction VL.

The seizing circuit does not extend over the seizing conductor 3 connected only to the final selectors NLW and RLW, but over the special seizing conductor 93 and the contact 1152 in this conductor. The switching operations described in section I are carried out.l On the selection of the marking digit for exchange connections the By the opening of contacts Iicl, the circuit over the relays I3 and M3 is opened. These relays do not .remain energised since on the closing of contacts l'2cl, I3cl the necessary negative potential is not connected to the conductors la and |b in the sub-exchange. 'Ihe relays I3 and M3 restore the arrangement in the main exchange to its normal condition.k

III. Setting up of a revertive'co'nnection by the subscriber TnN1 connected in the outgoing trunk Each junction VL is provided in sub-exchange with two revertive switching points RUI and RUZ. The first (RUI) serves for connecting the revertive line RL on initiation of an enquiry during an incoming exchange connection, and the second (RUZ) for connecting the enquiry line on initiation of an enquiry during an outgoing exchange connection. As revertive switching relay groups, relays Y| and Z are used for incoming exchange connections which are controlled by relay Xl and on outgoing exchange connections the relays Y2, Z which are controlled by the relay X2.

Since the subscriber TnNI is in an outgoing exchange connection the circuits of relays Y2 and Z are prepared at the contacts IllmZ, ||s2 and lph.

For initiating a revertive connection the subscriber TnNl momentarily presses the enquiry key RTI at his apparatus. Thus the subscribers loop is earthed. The differential relay X2, transmitting the revertive impulse, which is in series with relay A2 operates and completes the energising circuitfor'relay Y2: contacts |00m2, llsZ, |ll22, |03l, |042, |05wl, lph, relay Contact IU'lyZ is closed. Relay Z can however not operate since its winding I is shortcircuited over the contacts 021:2 and |03|. Contact ||a2 is short-circuited over contact |G8y2. Thus the impulses serving to determine the traic direction of the revertive connection (sub-exchange or main exchange) are prevented from operating arrangements in main exchange. By the opening of contacts |09y2, ||0y2 and the closing of contacts |||y2 and l||2y2 the talking conductors from the nal selector N'LWI are switched over at the revertive switching station RU2 to the revertive path RL.

The subscriber releases his revertive enquiry key RTI. The relay X2 restores. The contact |022 is opened. The short circuit for winding I of relay Z is removed. Relay Z operates and opens contact Inde and closes contact H32. Both windings I and II of the relay Z are now connected in series. Parallel to winding II of relay Z the relay Y2 is connected over contacts lllph. |wl, ||4x2, |U3l.

Choke Dr3 is connected over contacts ||5i2, H62, |||.w| in shunt across the talking conductors 0f the revertive enquiry line RL. The preselector RVW on this line in the local network hunts for a free final selector RLW.

A contact H92 a further circuit is prepared for the rotary magnet DML of the discriminator and at contact 83a relay E is connected: magnet DML, relay V, contact 53kml, winding I of relay E, contacts 21H2, 83e, 80h, 8|s2, Magnet DML and relay V do not operate. At contact ||8e the circuit for rotary magnet DML is further prepared.

The rst numerical impulse train transmitted by the enquiring subscriber serves to mark the exchange to which the required subscriber is to be connected. The impulses of this train are transmitted by means of the contact ||5i2 of the impulsing relay in the impulse receiver of the revertive enquiry path. 'I'hose impulse trains which serve to determine only the traffic direction are suppressed in the final selector RLW the position of which is not adjusted thereby. If the revertive enquiry path` extends over a group selector to which, for example, cross connections to other sub-exchanges which can be reached directly are connected, then by means of these numerical impulse trains the first group selector is positioned and corresponding to the number of effective impulses over a free final selector RLW, a cross connection outgoing to another sub-exchange or on selection of the marking digit of the main exchange a free contact is seized.

By means of the impulses of the rst impulse train sent out from the subscriber for the purpose of setting up a revertive enquiry connection the discriminator is also positioned since on each release of the relay I2 the circuit of the magnet DML is completed: contacts ||9z, ||8e, 6|z'2, relay V, rotary magnet DML,

During the positioning of the discriminator the contact 21h) is open, but relay E remains energised in the circuit: contacts 8|s2, 80h, 832, 62u, relay E, Winding'II, Thus the relay is prevented from energising over the wipers of the discriminator during the positioning opera- .tion at the end of the rst impulse train since relays A2 and I2 remain energised and relays V and E restore,

The discriminator differentiates between different impulse trains received and thus determines whether the revertive connection is to be setup over the revertive enquiry switch (RU2) in the sub-exchange or over a revertive enquiry switch in the main exchange.

If the required subscriber is connected to the sub-exchange of the revertively calling subscriber or any-subexchange which can be reached lconnection is set on a free contact. A switching operation is not initiated in this case.

If, on the other hand, impulse trains corresponding to the marking digits of the main exchange are effective, the revertive enquiry switching in the sub-exchange is discontinued, and revertive enquiry switching Yoperations are carried out in the main exchange. For this purpose, the relay W| is used with the relay W2 controlled by this relay.

-Relay WI is energised: contacts |202, 64e, wiper ML/V, contact |2|, winding I of relay Wl, and closes the contact |22w| in the circuit of the revertive enquiry switch relay group parallel to contact |0'Iy2 and thus ensures that relay Z is maintained energised. At contact |05w| it disconnects relay Y2 and locks up over contact |23w| and winding II in a holding circuit: contacts ||J0m2, |0|s2, |22wl, relay Z, winding I, contacts |03l, ||42, |23wl, relay WI winding II,

Relay Y2 restores. At contacts |||1/2, ||2y2 it disconnects revertive enquiry line RL and at contacts |09y2 and ||0y2 connects the revertively calling subscriber TnNI with the junction VL again. By the opening of contact |8y2 the short circuit for the impulse contact ||a2 is removed.

At contact ||'|w| the directcurrent bridge between the talking conductors of the revertive at contact 13e.

Thus the switching operation resulting when a connection is set up at the revertive enquiry position RU2 in the sub-exchange is released.

For carrying out the revertive enquiry connection in the main\exchange the circuit existing over the conductor la of the junction VL is momentarily broken. This interruption takes placeat contact-3910i. At contact |34w| further closing of this circuit and hence switch* ing through of the conductor la is prepared.

On the opening of contact 39w| the relay M3 restores in the main exchange and connects relay X3 controlling the revertive enquiry switch relay group Y3, ZI: contacts 43h, 4253, |24el, |25m3, relay X3, Relay X3 closes energising circuits for relays P3 and Y3: contact 2603, relay P3, contacts 2722I, 2'I3x3, 23114, -I-, in nal selector LW2 and contacts |251), |2323, |2924, relay Y3,

Relay P3 at contact 29213 locks up and at contacts 30223, 3Ip3 switches through the conductors of the nal selector LW2 and at contact 32233 connects relay PHI.

The relay YS closes the Contact |2'Iy3. The relay ZI however cannot operate since its wind` ing I is short circuited at contact |2B3. At con tact 931/3, the holding circuit extending over winding II of relay UI is opened. Since relay UI restores, the exchange line is disconnected at contacts Stul, 9`Iu| and connects the iinal selector LW2, by closing contacts Mul, 9511A, to the junction VL. The exchange connection is thus maintained since the choke DrG is connected over contact |33y3 between the talking conductors extending to the exchange selector AW.

When, in the subexchange, the slow-to-operate relay W2 connected by relay WI has energised, contact 33u22 is opened and contact I33w2 closed and the conductor Ie of the junction is again switched through. The relay M3 in the main exchange again operates and disconnects relay X3. The contact |2x3 is opened and the contact I353 closed. The relay ZI operates: contacts IZGb, I2'Iy3, relay ZI winding I, contact I 292| relay Y3, Contact I29e| is opened and at contact |35e| the winding II is connected. Relay YS is connected over contact I35zr3 in parallel with winding II of relay Z| and remains energised for a further period. The contact 99e! in parallel with contact |3||y3 in the holding bridge for the exchange line is closed.

The impulses transmitted from the calling subscriber for setting the final selector LW2 are repeated from the relay A2 by means of contact ||a2 to relay I3 and thence. by means of contact'dSiS to the impulse receiving arrangements of the nal selector LW2.

The relay W2 in the sub-exchange energises and `causes the discriminator to be stepped-on to its normal position. At contact 2'I4w2 the homthe v ing circuit is closed: contacts 8|s2, 80h, 2141112,

18e, dlcml, relay V, rotary magnet DML, Over contact SSdml winding II of relay E is connected and opens the circuit for magnet DML Magnet DML and relay E are alternately energised until the discriminator has reached the home position in which contact fllcml is opened and contact 53km| closed.

For setting up the exchange connection again when the revertive enquiry connection is iin- H4122 disconnects relayy WI (contact |042 is opened). Relay WI opens contact |34w| and closes contact 39wI. In the main exchange HZ relay M3 restores and over contact |25m3 causes relay X3 to enereise. Bv the opening of Contact |3323 relay Y3 is disconnectedand at contact |28x3 winding I-of relay ZI is short-circuited. Ovel,` the contact |,233 the relay Z! (winding AII) is still maintained energsed. when` on the release .of relay YS the Contact IZlyS is opened. The contact ISM/3 in theholcling bridge of. the eX- change lneis opened. At contact 931/3 the circuit over the Winding II of relay UI is closed.

The relay UI disconnects the final selector LW2 and connects the junction VL to the conductors extending to the exchange selector AW again.

In addition to the switching operations already described relay- X2 in the sub-exchange brings about the disconnection of Winding I of relay Z at contact |22w| and the -completion of a holding circuit over the winding II of relay Z at contact |022. i

On the release of relay WI the slow relay W2 is disconnected at contact I32wI. When this restores after some time, and its contact |33w2 is .opened and contact 38102 closed, the conductor la is again switched through and the relay M3 in the main exchange operates.

The relay X3 is disconnected. At contact |281c3 the holding circuit'of the winding II of relay ZI is opened. After the release of relay ZI the revertive enquiry switch relay group of the main exchange is again in the normal position. The holding bridge over Dr which maintains the exchange connection over the revertive en.- quiry is disconnected as now contact 992| is opened. The discontinuing of the revertive enquiry switch operation and the further setting up of the exchange connection of the main exchange therefore occurs independently of the termination of the switch operations by the subscriber TnNI.

When the subscriber TnN I in order to set up the exchange connection again releases the enquiry key RTI the relay X2 restores. At contact I022 the holding circuit over the-winding II of relay Z is interrupted. When the relay Z has restored theA revertive enquiry switch relay group of the sub-exchange consisting of the relays Y2,

Z, WI W2 is restored.

1V. Setting up an exchange connection to subscribers of the sub-exchange UZ The operator receiving the call over the exchange line AL when a subscriber of the sub-.- exchange UZ is required actuates the selector key WS (Fig. 4) associated with the free junction to this sub-exchange. The relay W3 associated with the junction VL and the relay W4 common to all junctions are energised. The re,- lay W3 disconnects conductor Ib at contact |6w3 and by closing contacts |88w3 and |89w3 connects the branch to the impulse sender at the junction line VL. The relay NT is also energised: I3'Iw3, |331?, relay NT, and in known manner brings about the positioning of the exchange selec'tor AW on the calling exchange line AL. The relay RI is energised: contacts news, mem, met, Arelay ai, Winding 1, At contact Ill2r| relay CII (winding I) is connected. By the opening of contact |8504 the junction is guarded against seizing over selector NLW2. Over the winding II of relay C4 a holding circuit is set up extending over winding I of relay C3: contacts |4303, 14'113, |4811, winding I of relay C3,

contact |4904, |5|Jw3, winding II of relay C4, In view of the closing of contact l |c3 and opening of contact |4603 relay B operates over its winding II. It opens contact |481) and closes contact |521). At contact |8|b the relay N is energised and at contact |8311 prepares a circuit for relay V4.

At contact 31H the conductor la is interrupted and at contact |4311 a circuit is set up over the conductor la to the sub-exchange UZ: A. C. source, relay II|, contacts |43rl, M4114, conductor la, contacts 38w2, 3910i, |2c|, M5292, and llph, condenser, relay R, In this circuit however relay R operates and connects relay H'. contacts |5612, |511', relay I-I, winding I, At contact |58h the circuit of relay E is closed: -i, contacts I59m2, |58h, 21h), Winding I of relay E, contact 53lcml, relay V, rotary magnet DML, V and DL are not energised in this circuit. At contacts |9 le and |9271. the setting circuit for the discriminator is prepared. At contact 2|2h the reply circuit is prepared which is closed on the reply of a selected subscriber of a sub-exchange.

In the main exchange relay B closes a circuit over the conductor lb of the junction: choke D18, contacts lli/4104, ns1', |5151u4, |5312, |89w3, conductor Ib, contacts |3c|, lph, |6Isl, relay I, Relay I by opening contact S1' guards the junction VL against seizing over a selector of the sub-exchange and connects the test relay P2 which determines whether the selector LWI is ready to operate: contacts |62sl, |631', relay P2, winding I, contact |64d1l, conductor pl, rotary off-normal contact ||5wlw of the final selector LWI, Simultaneously at contact |661 relay Il is connected and at contact |1811 removes the short circuit for winding `II of relay P2 and at contacts |6111 and |6811 switches through the talking conductors to the final selector LWI.

The relay A (iinal selector LWI) and relay Al (junction line VL) operate: winding I of relay A, contacts |69p-I, |6111, lltr, winding I of relay Al, contact |||s|, winding II of relay AI, contacts |6811, |12pl, winding II of relay A, l-. Relay A| at contact 239a| connects the relay I2 which transmits impulses for setting up a revertive enquiry connection, while relay A prepares the nal selector LWI to receive impulses. Contact ZillaI is opened.

Relay P2 has opened contact |45p2 and at contact H3102 switched through the conductor la. Thus a circuit to be described later is completed over the conductor la of the jlunction. The contact I'I4p2 parallel to contact lph in the conductor lb is closed. At contact |95p2 relay PH (winding I) is connected and opens contact |60ph is nally disconnected from` the conductor la over contact |`|6ph connects its own winding II to the conductor la. The relay P2 also completes the seizing circuit over the relay C of the nal selector LWI: contact |11p2', winding II of relay P2, conductor bl, winding I of relay C, off-normal contact |197clw of final selector, Relay P2 remains energised over this circuit until the termination of the connection. Relay C prepares at contact |99c a holding circuit over its winding I and II which becomes eiective after the opening of contact |'l9kl1u on the first vertical step of the iinal selector.

In the circuit set up after the energisation of relay P2 by the closing of contact |13p2 over the conductor |a: l, relay DTI, contacts |8|Jm|, H3112, |2cl, 39wl, 38102, conductor la, contacts 144124, |4311, relay HI, relays DTI vand HI operate.

in the conductor Ib. At contact l'iph. relay R,

seins The relay HI at contact |40h| opens the cir-A cuit for relay RI' (winding I) which restores. Relay V4 operates: contacts |8211, |8311, 2||a3, relay V4, resistance 2|, At contact 22124 a holding circuit is completed for relay B over its winding I. The relay V5 is short-circuited and does not operate. After the closing of the contact 3`ir| in the conductor lathe relay M3 to which minus is connected over resistance |86 and contact |81c3 is energised.

The operator of the main exchange now transmits impulses for positioning the selector LWI on the required subscribers line. During the operation the talking apparatus Be is short-circuited-at contact nsa. At the same time the resistance |94 is connected parallel to the choke D'r8. The impulse contact 1131' on the operation of the dial switch interrupts the circuit of the impulsing relay I of the sub-ex-change which repeats the impulses by means of contact |661 to the relay Il. By means of the contacts |6111 and |681| the impulses are transmitted to the impulsing relay A of the nal selector LWI. At contact |9011 on each release of relay Il the rotary magnet DML is connected: contacts |93p2, |92h, |9I'e, |9011, relay V, rotary magnet DML,

The rst impulse train transmitted from the operator by which the first selector is positioned on a line group determines whether the required subscriber is authorised for exchange connections (private station) or not (public station). In order to evaluate these impulse trains and thus to mark the traffic facilities the discriminator is used again.

If by means of the positioning of the discriminator it is determined that a group of private subscribers has been selected, then at the end of the impulse trains when the relay E, energised during the setting operations of the discriminator, over its winding II and contacts 6211, |58h |59m2, restores, a switch operation is not initiated over the discriminator.

If however by means of the first impulse train the wipers of the final selector LWI are set on a contact; group in which subscribers not having facilities for exchange connections are included i. e. public stations, then the wiper ML/I-I of the discriminator rests on contact |98. The cut7 off relay Tr operates: contacts |96p2, I91h, 63e, wiper ML/H, contact |98, relay Tr, At contact |`|0tr the circuit over the relays AI and A is interrupted, and both relays restore. The seizing relay C in the final selector LWI is shortcircuited at contact 20|a. The contact |990 is opened and `thus the holding circuit over the winding II of relay P2 is interrupted. The contacts |13p2 and |14p2 are opened. The winding I of relay PH is disconnected at contact |95p2 but relay PH remains energised in the circuit which extends over its winding II, the contacts 2221:, I'lph., |45p2, conductor la and relay M3, and by keeping the contact Eph open guards the junction VL against seizing over a selector of the sub-exchange. The relays I and DTI restore.

In the main exchange relay Dr8 restores and connects the signal (a lamp) by which the operator is informed. thatv the required connection cannot be set up since the subscriber selected is not permitted facilities for exchange connections and therefore she connects herself once more with the calling exchange subscriber.

In the sub-exchange the release of relay P2 results in the release of relay I-I since its holding circuit is open at contact 202122. At contact 80h the circuit for releasing the discriminator is completed. The relay V energised during the release movement of the discriminator holds relay PH energised: winding II of relay PI-I, contacts 22311, 2353/2, When the discriminator reaches its zero position relay V restores and thereupon relay PH which is now no longer connected over conductor la, since, in the meantime, in the main exchange negative has been disconnected from relay M3, which restores. This takes place in that when the selector key WS is set back to normal the relay W3 restores and, at contact |39w3, interrupts the circuit over the winding I of relay N. Relay N restores since the holding circuit over its winding II and conductor Ib is open in the sub-exchange at contacts I 602m and I'I4p2. At contact IBIIn, the Winding II of relay C3 and at contact |911. the relay V4 are short-circuited and the relays C3 and V4 restore. Relay C3 disconnects negative from relay M3 at I8'Ic3, and at contact 221:4 the relay B is disconnected.

On the determination of the exchange traffic facilities of the subscriber reached over the selected line group in the nal selector, the relay Tr is not energised. By means of the second impulse train the wipers of the nal selector LWI are set on the contact of the required subscribers line. The positioning of the discriminator by means of this impulse train does not occur since Contact I9 Ie is opened.

The discriminator remains in the position which it took up on the nrst impulse train since the relay H maintains its homing circuit open at contact Bh.

When the nal selector LWI has been set and the selected line is free only the test relay P of the two series relays P and PI operates and brings about the known switching operations. Contacts 2051: and 2p are closed. At definite time intervals, for example, every 10 seconds, a call relay not shown is energized which opens contacts 207W and over contact ZBBTT connects a ringing current source'. If the subscriber TnNI replies in a call pause relay Y operates and disconnects the call relay. At contact 29y the relay U is connected and closes the reply circuit: I,. Contacts 2 Isp, 2 I lu, winding I of relay PI, conductor ml, contact 2I2h, windings I and II of relay MI,

The relay PI of the final selector opens contacts IBSpI, I'I2pl, 2I4p, 2I5pl, and closes 2I6pl and 2IIpl. The talking conductors in the final selector are metallically switched through. The subscriber TnNI receives feeding current over the bridge across the junction line (relay AI). Relays A and Y restore. Relay C is not shortcircuited since the contact 200m is opened. Relay U restores and at contact 2l lu interrupts the .circuit transmitting the reply signal to the apparatus on the junction. The winding I of relay PI is thus disconnected. This relay further holds over its winding II in locking circuit.

The relay M! energised on the coming into effect of reply signal short-circuits its winding I at contact 2I3m| and therefore restores slowly on the resulting interruption of the circuit (at contact 2| Iu) At contact 2I8ml the relay SI is connected and by means oi contact ISml reply signal is transmitted to the main exchange by momentary opening of the circuit over the conductor Ia.

The relay SI locks up at contact 22IsI and at contact 23sl opens the holding circuit for relay H which at contact 8011. closes the previously described homing circuit for the discriminator. The

of relay RI,

bridge relay AI is operated. By the opening of contact I'IIsI the direct' connectionof the two windings I and II is discontinued. At contact Z'Isl the winding I of relay XI connected with minus is connected to the winding I of relay AI and at contact 220sI v.the winding II of relayv XI connected with plus is connected to the winding II of relay AI. yThe relay XI does not operate in the microphone feeding circuit since it is a difference relay. Y

In the main exchange the relay M3 is operated by the momentary interruption of the current over the conductor. It connects relay RI: -I-, contacts 22504, 226114, 22'Im3, 228s3, windingII This circuit is interrupted by the further energisation of relay M3. A.During the release .period of relay RI relay S3 is energized; -I, contacts 22904, 23011, 4Im3, relay S3, Relay S3 locks up in a circuit extending over its contact 4253.

'Relay UI operates since the operator has. al-

ready set back the selector switch WS to its normal position and the relay W3 has restored; I-, contacts 89w3, 2325-3, 233ml, 931/3, winding II of relay UI, at contacts QBuI and S'Iul with conductors extending to the positioned exchange selector AW and at contact 94u| and 95u| ldisconnects the access means to the nal selector LWZ. to the winding II of relay UI is the winding II of relay El which also operates.

After the switching through of the junction VL to the exchange selector AW the bridge relay .S4 in the exchange line AL operates and brings aboutthe known switch operation on the exchange line whereby the maintenance of the exchange connection is made dependent on the subscriber of the sub-exchange UZ.

V. Setting up a revertive enquiry by vthe sul)r seriber TnN1 called in an exchange commotion contact IIph and forthis purpose at contact 2361071. connects the relay YI controlling therevertive enquiry switch station RUI on incoming exchange connections. In order that during the impulse transmission over the junction necessary for a revertivegenquiry connection to a subscriber of the main exchange the relay II will not be controlled by means of the relay I, connected in the impulse circuit over the conductor Ib, impulse contact |662' in its circuit isV short-circuited by means of contacts 23Isl and 238drl. I2 connected at .contact 239a| repeats the numerical impulses which the subscriber transmits for setting up the revertive enquiry path to the numerical impulse receiver of the sub-exchange and tothe circuit of the rotary magnet of the discriminator.

After initiating the revertive enquiry connection the subscriber TnN I operates the enquiry key RTI for a short time. The relay XI operates and connects relay YI: contacts 2Mp2, 242m, |042, Iwl, 236ph, relay YI, The relay YI by opening contacts 2431A, 244y| disconnects the junction VL from the connecting path to the en quiring subscriber and connects the latter over contacts Zyl and 2463A at the enquiry line RL. At contact 24h/I the impulse Contact 248m is bridged over and thus the rst numerical impulse train by which'it is determined whether the re- Relay UI connects vthe junction VL` Parallel The relayA vertive enquiry connection is to be transmitted over the selector of the main exchange or over the selector of the sub-exchange is prevented from reaching the main exchange. The contact 249y| in the circuit of the winding I of relay Z is closed. Relay Z cannot operate since its winding I is short-circuited at contact 242ml.

When the calling subscriber releases his enquiry key relay XI restores, contact 242ml is opened and contact I|l3r| is closed. Relay Z operates and with its contact I |32 locks up over its winding II. Relay Y| also remains energlsed since it is connected parallel to winding II of relay Z in series with its winding I: relay YI, contacts 236p^h, ||l5w|, H4922, I03.'1:|, winding I of relay Z. At contact |I6z the choke D13 is connected in shunt between the talking conductors in the revertive enquiry line RL. The revertive enquiry preselector RVW operates and seizes the free iinal selector RLW to be used for revertive connections.

The discriminator positioned by the rst impulse train sent out from the calling subscriber determines the trailic direction of the revertive enquiry connection (to the sub-exchange or to the main exchange). If the main exchange is marked relay WI is energised again and disconnectsrelay YI at contact I05wl. Contact 24h/I is opened and thus the short circuit for the impulse contact 248a| is removed. At contacts 243y| and 244y| the talking rline is switched through to the main exchange and by the open` ing of contacts 245yl, 246y| the revertive enquiry line RL is disconnected.

The relays WI and W2 operating one after the other, as described previously, transmit the marking signal consisting of a momentary interruption of the circuit over the conductor Ia for determining the revertive enquiry switching operation in the main exchange.

This marking signal is received by relay M3 which brings about the disconnection of relay UI and hence the connection of the final selector LW2 to be used for the revertive enquiry connection. The energising circuit of relay P3 is closed bya relay Y3 at the contact 25|y3 which is in parallel with Contact 2603.

The discontinuing of the enquiry connection and setting up of the exchange connection again takes place in the usual manner on the momentary pressing of the impulse key. The impulse for -discontinuing the revertive enquiry connection is transmitted to the main exchange by the successive restoration of relays WI and W2 momentarily interrupting the conductor Ia. All these operations are explained in detail in section III so that further explanation at this point is not necessary.

VI. Connection between subscriber TnNZ, main exchange, and subscriber ITnNI, subemchange On the setting of the nal selector NLW2 on a free outgoing junction VL to the sub-exchange, relays P5 and C3 in the test circuit operate: test relay P5, wiper 252, contacts 253, |85c4, parallel windings I and II of relay C3, contacts |4812, |4113, |4603, The two windings I and Il of relay C3 are connected in opposite senses so that relay C3 operates slowly and actually only when, in the final selector NLW2, the talking conductors are metaliically switched through and the bridge relay A3 of the seized access means to the junction is energised in the microphone feeding circuit. At contacts 26Ia3 and 262c3 the .access means to the conductor Ib ofthe junction is switched through and at contact |8'Ic3 negative potential is connected to the relay M3. By the closing of contact I5|c3 relay B (winding II) is connected and operates since contact |46c3 is open. At contact |48b winding I of relay C3 is disconnected and at contact |521) the release of the junction is prepared at the termination of the conversation. The winding II of relay C3 is now not short-circuited since contact 263a3 is open. At contact 2lb the relay KI is connected and at contact 264m the choke Dr4 connected to minus is extended to the conductor Ib.

A circuit is now set up over the conductor Ib of the junction and relay I in the sub-exchange: choke DM, contacts 264m, 26Ia3, 265c4, y26204, |6103, conductor Ib, contacts |3cI, I60ph, ISISI, relay I, Relay I at contact |661' connects relay II and closes the circuit extending over the test line pI for the relay P2 which operates and closes contacts H3112 and I'I4p2. Relays DTI (UZ) and M3 (HZ) now operate: relay DTI, contacts |80mI, H3112, I2cI, 39ml, 38102, conductor Ia, contacts 31r| relay M3, contact I8lc3, resistance |86, In the sub-exchange at contact |p2 the winding I of relay PH is connected.

In the main exchange the connection of relay B results in the connection of relay V4: contacts 26617, 26a3, relay V4, resistance 2|,

The impulses transmitted from the subscriber TnNZ for setting the nal selector LWI on the junction of the required subscriber are repeated from relay A3 by means of contact 26Ia3 to the impulse accepting relay I. The transmission of the impulses to the iinal selector takes place in the manner described. A positioning of the discriminator by means of the impulses for setting up the incoming local connection does not occur since relay H which is only energised when the alternating current impulse initiating an exchange connection is effective is in its normal position. r

I claim:

1. In an automatic telephone system having a plurality of exchanges, trunk lines connecting a pair of said exchanges, subscribers lines in one of said exchanges some having facilities for inter-exchange calls and others having facilities for only local calls, a discriminating switch for each trunk line operated on all calls between said exchanges over said trunk lines, means associated with said trunk lines for completing revertive inquiry calls in either exchange on calls over the trunk line in either direction, and means controlled by said discriminating switch for preventing'exchange calls to subscribers not entitled thereto and also for controlling all revertive calls.

2. In a telephone system a pair of exchanges a trunk line connecting the two, subscribers lines in one exchange entitled to high valued calls and others only to low Valued calls, a discriminator switch associated with said trunk in said one exchange and operated during the extension of calls over said trunk line, means associated with the trunk line for extending high valued calls and revertive inquiry calls in either exchange, means operated in one position of the switch for permitting or preventing high valued calls dependent on the line calling, means operative in another position of the switch for controlling inquiry calls in one exchange, and means operative in another position of the switch lfor permitting or preventing calls of high value dependent on the line called.

3. In a telephone system, a trunk line extending between two exchanges, means for extending calls in either direction over said trunk line, a discriminator switch in one of said exchanges, said switch operated in calls over said trunk line, certain of the lines in said one exchange having facilities for high valued calls and others for only local calls, means controlled in one position of the discriminator switch for preventing calls to the other exchange from lines not having the proper facilities for such calls, and means controlled in another position of the switch for preventing calls from the other exchange to lines having facilities for only local connections.

4. In a telephone system, a trunk line extending between two exchanges, means for extending connections over said trunk line in either direction, said trunk line terminating at each end in automatic switches for extending such connections, other branches associated with said trunk line in each exchange for connection therewith to complete inquiry calls, a discriminator switch associated with said trunk line in one exchange and operated in calls in both directions thereover to control the extension of inquiry calls over said branches.

5. A telephone system as claimed in claim 4 in which there are certain subscribers in one exchange having means for effecting inquiry calls by means of said branches and other subscribers not having such means.

6. In a telephone system, an inter-exchange trunk line, means for extending connections in either direction thereover, branches at each end of said trunk for seizing the same, other branches for each end thereof containing switches for extending connections therefrom, other branches for extending revertive inquiry connections from the trunk line, and a discriminator switch associated with said trunk line and operated by impulses transmitted to the trunk in connections thereover in either direction to control the extension of connections over said branches.

7. In a telephone system, a two Way trunk line extending between two exchanges, subscribers lines in one exchange divided into two classes, branches associated with said trunk lines and available to subscribers of only one class for connection with said trunk lines for making re- Vertive inquiry calls when connections are extended over said trunk line, a discriminator switch associated with said trunk line in said one exchange, said switch operated in calls over the trunk line in accordance with the destination of such calls to render said branches available for revertive calls. 

